2.4. Measurement of Lactate Dehydrogenase Levels
The level of lactate dehydrogenase (LDH) released from the cells was
measured using an LDH assay kit (A020; Nanjing Jiancheng Biology
Engineering Institute, Nanjing, Jiangsu, China). VSMC-derived foam cells
were treated with 0, 1, 10, and 100 μg/mL ox-LDL for 24 h. The cell
supernatants were collected for analysis. Matrix buffer, coenzyme I, and
2,4-dinitrophenylhydrazine solution were added to the samples, which
were then incubated at 37°C for 15 min. The reaction was then terminated
by adding an appropriate amount of 0.4 mol/L NaOH solution. The
absorbance of the sample was determined at 450 nm using a microplate
reader (LabX, Austria).